Although various known clinical analyzers for chemical, immunochemical and biological testing of samples are available, clinical technology is rapidly changing due to increasing demands in the clinical laboratory to provide new levels of service. These new levels of service must be more cost effective to decrease the operating expenditures such as labor cost and the like, and must provide shorter turnaround time of test results to reduce the patient's length of stay in the hospital as well as improve efficiency of outpatient treatment. Modernization of analytical apparatus and procedures demands consolidation of work stations to meet the growing challenge placed on clinical laboratories.
Generally, analysis of a test sample involves the reaction of test samples with one or more reagents with respect to one or more analytes wherein it is frequently desired that the analysis be performed on a selective basis with respect to each test sample. However, due to the high demands placed on clinical laboratories regarding not only volume throughput but also the number and frequency of various analyses, there is a need to provide an automated analysis system which is capable of combining accurate analytical results, high throughput, multiple test menu versatility as well as low reagent consumption.
Typically, analysis of a test sample involves forming a reaction mixture comprising the test sample and one or more reagents, and the reaction mixture is then analyzed by an apparatus for one or more characteristics of the test sample. Reliance on automated clinical analyzers improves the efficiency of the laboratory procedures inasmuch as the technician has fewer tasks to perform. Automated clinical analyzers provide results much more rapidly while frequently avoiding operator or technician error, thus placing emphasis on accuracy and repeatability of a variety of tests. Automated clinical analyzers presently available for routine laboratory tests include a transport or conveyor system designed to transport containers of sample liquids between various operating stations. For example, a reaction tube or cuvette containing a test sample may pass through a reagent filling station, mixing station, reaction forming station, detection stations, analysis stations, and the like. However, such transport systems are not flexible in that transport is in one direction and the reaction tubes or cuvettes, once inserted into the apparatus, must pass through without access before analysis occurs.
Automated immunoassay analyzers have been provided such as the Abbott IMx.RTM. analyzer and the Abbott TDx.RTM. analyzer (Abbott Laboratories, Abbott Park, Ill., USA) which utilize procedures involving a variety of different assay steps but typically rely on detection and measurement of optical changes in a reaction mixture during the assay process. For example, a number of well-known techniques using single or multi-wavelength fluorescence include fluorescent polarization immunoassays (FPIA) employing homogeneous immunoassay techniques, microparticle enzyme immunoassays (MEIA) employing heterogeneous immunoassay techniques, and the like. The MEIA technology, such as that used on the Abbott IMx analyzer, is used for high and low molecular weight analytes requiring greater sensitivity, and FPIA technology, such as that used on the Abbott TDx analyzer, is used primarily for lower molecular weight analytes. A front surface fluorometer is used to quantify a fluorescent product generated in the MEIA assays, while a fluorescence polarization optical system is used to quantify the degree of tracer binding to antibody in the FPIA assays. The test samples are automatically processed in the Abbott IMx analyzer and Abbott TDx analyzer by a robotic arm with a pipetting probe and a rotating carousel which positions the samples for processing. These instruments are compact table-top analyzers which offer fully automated, walk-away immunoassay testing capabilities for both routine and specialized immunoassays. These nonisotopic methods eliminate radioactivity disposal problems and increase reagent shelf life while meeting the diverse requirements of a multitude of different assays.
Instead of loading the test sample into a container and obtaining sequential testing, such as one direction only systems as described above, the Abbott IMx analyzer and the Abbott TDx analyzer, often referred to as batch analyzers, permit the analysis of multiple samples and provide for access to the test samples for the formation of subsequent reaction mixtures. However, such batch analyzers permit only one type of analysis at a time. In a random access analyzer, not only can multiple test samples be analyzed, but multiple analytes may be analyzed from each test sample. Another common feature of presently available sequential and random access analyzers is the inclusion of various reagents within the apparatus itself or placed near the apparatus for pipetting purposes. Liquid reagents, in bulk form, are selected for the various types of tests which are to be performed on the test sample, and are stored in or near the apparatus. The reagent delivery units, such as pumps and the like, along with valves, control and pipette mechanisms, are included in these automated analyzers so that different reagents can be mixed according to the type of test to be performed. The Abbott IMx analyzer automatically performs all the steps required for analysis of test samples and includes numerous checks of the subsystems to insure that the assay can be run to completion and that results are valid. Quantification of the fluorescence intensity in the MEIA method and polarization in the FPIA method, as well as the final data reduction, are also fully automated on the analyzer. Results are printed by the analyzer and can be accessed through suitable means for automatic data collection by a laboratory computer.
Automated analytical apparatus for performing homogeneous assays, the detection of precipitate formed by reaction between antigens and antibodies in a test sample cell to form light scattering centers, and methods and apparatus for detecting immunological agglutination reactions are also known in the art. Such apparatus and methods include, for example, the steps of measuring light absorption of the liquid medium with antibody before and after the antigen-antibody reaction by using light which is absorbable by the antibody, and calculating the difference of the absorptions. In this way, the presence or absence of agglutination can be detected based on the fact that the agglutination reaction reduces the concentration of antibody, which affects the light absorption of the liquid medium. As is typical of methods and apparatus for performing homogeneous assays, these procedures do not require separation of a solid phase from the reaction mixture for further analysis.
Heterogeneous assays are also known through the use of a sample analyzer for quantitating relatively small amounts of clinically significant compounds in a liquid test sample by focusing a light source onto the sample so that, for example, fluorescent particles in the sample cause fluorescent conditions, the intensity of which is the function of the intensity of the light beam and the concentration of fluorescent particles in the sample. A detector senses photons forming the fluorescent emissions of the particles when excited by the light beam. The introduction of a solid phase material into the sample requires subsequent separation of the solid phase from the reaction mixture for further analysis and before the fluorescent emissions can be detected and measured.
Recently, apparatus and methods have been proposed for performing, selectively on the same sample, various homogeneous and heterogeneous assays concurrently in a random access fashion. Such apparatus and methods provide for the analysis of a plurality of liquid samples wherein each sample is analyzed with respect to at least one analyte utilizing both homogeneous and heterogeneous assay techniques.
Accordingly, since such previously described automated analyzers do not contemplate an automated analytical system for simultaneously performing both homogeneous and heterogeneous assays in a continuous and random access fashion utilizing a commonality of various process work stations and transfer means, there is a need to provide an automated analytical system having these features and sufficient flexibility to meet the growing needs of the modern clinical laboratory.